Research and Optimization of Σ-Δ Modulator at High Temperature

Analog-to-digital converters (ADCs) are widely used as a bridge between analog and digital domains in communication systems. With the rapid development of smart sensors, the demand for high-precision ADCs is increasing day by day. In recent years, ∑-A modulators have been widely adopted in high-performance ADCs owing to their high resolution and strong noise immunity. However, extreme high-temperature working environments such as aerospace and oil exploration place higher requirements on the working performance of modulators at high temperatures. To address the issue that traditional high-order $\Sigma-\Delta$ modulator systems tend to lose stability at high temperatures, this paper constructs an optimized high-order $\Sigma-\Delta$ modulator model. This model adds local negative feedback, gain control and other modules to the traditional fourth-order single-bit quantized modulator model to improve the performance and stability of the system at high temperatures. Aiming at the problem of time domain and frequency domain performance degradation of sampling switches in high temperature environments, this paper proposes an optimized circuit design scheme. This scheme significantly enhances the system's operational stability under high-temperature conditions through an improved sampling switch architecture. In the design of the sampling switch, a bootstrap structure is used to enhance the gate drive capability. At the same time, redundant transistors and virtual transistor technology are introduced to effectively improve the switching linearity and suppress the channel charge injection effect. The optimized modulator system is simulated. At 175°C, the SNDR of the modulator is 105.2dB and the ENOB of the modulator is 17.79bits. The simulation results show that the added optimized structure can effectively improve the performance of the modulator at high temperature.